Power management in appliances

ABSTRACT

An appliance, such as a set top box, has an ON power mode and a STAND BY power mode and is in communication with a television set. A parameter of an operating signal associated with the television set is monitored and the value of the parameter is compared with predetermined values at which the set top box is desired to be either operative (ON power mode) or inoperative (STAND BY power mode). When a predetermined value of the parameter is detected, the current power mode of the set top box is evaluated and, if necessary, changed. Power supply to the TV set, operating frequency of a local oscillator/mixer in the TV set or the presence of a line scan signal from the TV set rate can be monitored to determine whether the appliance should be turned on or off.

The present invention relates to improved power management in consumerappliances which output video signals for display through a users'television set, such as set top boxes (STBs).

STBs receive broadcasting signals from, for example, cable, digital orsatellite service providers. The signals are typically fed to a singlechannel of the associated television set. Other channels are typicallyreserved for terrestrial television signals, VHS/DVD players or gamesconsoles. Once tuned to the STB signal-receiving channel, a variety ofdifferent broadcast signals can be selected for viewing through thatchannel.

It will be appreciated that a significant amount of power is consumed bya STB when receiving a large number of broadcast signals from a serviceprovider, power that is wasted when none of the broadcasts are beingviewed or heard by a user.

In order to conserve energy, modern electronic appliances are commonlyprovided with a “stand-by” mode. When in this mode, the appliance isessentially switched off, except for a receiving circuit, which isconfigured to receive a reset signal, for example an infrared signalemitted by a remote control hand set. This mode enables energy thatmight otherwise be used to power the appliance, to be conserved withoutthe need for disconnecting the appliance from its main power supply.

It is known from U.S. Pat. No. 6,292,943 B1 to provide a power controlmethod for a STB. That method is specifically directed to signalling aSTB which is in a “stand-by” mode to switch on and to transmit abroadcast programme which has been selected for recording on a videocassette recorder (VCR). In the method, a VCR is programmed to record aspecified program at a specified time. When the VCR prepares to recordat the specified time, a signal is sent to the STB to ensure that theSTB is switched on and ready to relay the signal associated with theselected programme for recording by the VCR.

An object of the present invention is to reduce energy consumption of anappliance which outputs a video signal.

According to a first aspect, the present invention provides a powercontrol method for an appliance which outputs a video signal for displayon a television set, the appliance having an ON power mode and a STANDBY power mode and being in communication with the television set, themethod comprising;

monitoring a parameter of an operating signal associated with thetelevision set;

comparing the value of the parameter with predetermined values at whichthe appliance is desired to be either operative (ON power mode) orinoperative (STAND BY power mode); and,

evaluating, when a predetermined value of the parameter is detected, thecurrent power mode of the appliance and if this is not the desired powermode, initiating a change in operation of the appliance from its currentpower mode to the desired power mode.

In one simple embodiment, the operating signal is the electricity supplypassing through the power cord to the television set. Optionally, theparameter monitored is the electric current passing through the powercord. It will be understood that when the television set is switched onso as to display a broadcast programme, the electric current will besignificantly higher than when the set is switched off or in stand bymode. In such an arrangement, when a predetermined electric currentvalue, higher than that associated with the television set being off orin stand by mode is detected, operation of the appliance in ON powermode is initiated. When the electric current value falls below thispredetermined value, the operation of the appliance is switched to standby mode. Thus, the appliance can be configured to switch to its ON mode,automatically, when the television set is on, or to its STAND BY modewhen the television set is switched off or to stand by. It is to beunderstood that whilst the specific example of current is given here,with suitable sensors, other variable parameters of the electricitysupply could be monitored without materially affecting the mode ofoperation of this embodiment.

This first embodiment of the method may be effected by a suitablyadapted electrical socket into which the power cable of the televisionset is plugged and which is in electrical communication with acontroller for the appliance. Sensors in the socket monitor a chosenparameter (e.g. current, voltage or resistance) passing to the powercable and the television set, when the sensors detect that apre-determined value, for example, of the electric current has beenreached or exceeded, this information is relayed to the controller whichin turns signals the appliance to power up to full ON power mode.Conversely, when the sensors detect that the current monitored hasfallen below the predetermined value, the controller signals theappliance to power down to STAND BY mode.

In an alternative embodiment, the operating signal monitored is thefrequency of the oscillator/mixer of the television set. One particularfrequency will define the channel through which the services received bythe appliance are carried to the TV. When this pre-determined frequencyis detected, the appliance is operated in full ON power mode, when thefrequency is other than the pre-determined frequency, the appliance isoperated in STAND BY mode.

Such an embodiment of the method can be effected with the use of an RFcable connecting the controller of the appliance with the televisionset. Leakages down the RF cable can be monitored for occurrences of thepre-determined frequency. Detection of the pre-determined frequencysignals a controller of the appliance to operate the box in ON powermode. Detection of a different frequency, or zero frequency, signals thecontroller to operate the box in STAND BY mode.

In another alternative embodiment, the operating signal is the line scanof images displayed on the screen of the associated television set(having a cathode ray tube display). Thus, the predetermined ‘value’ maybe the presence or absence of a line scan. Magnetic field detection canbe used as a means of detecting the line scan rate.

In a more complex version of this embodiment, line scans may incorporatesignatures which can be recognised by a controller of the appliance asrelating to a broadcast made by the service provider whose broadcaststhe appliance is configured to receive. The “parameter” monitored wouldbe a signature of the line scan. Thus, in this more complex version, theappliance is configured to operate in ON mode only when the televisionset is on and the viewer is viewing a programme received through theappliance.

The signature of the line scan may be a subtle alteration of the timingand/or frequency of the line scan associated with a particular serviceprovider. An alternative arrangement is possible, with the signature ofthe line scan being a n appliance generated signal. In this embodiment,even if there are multiple pieces of equipment connected to the TV (suchas STBs, games consoles etc.) each one can uniquely identify it's ownsignal. In a digital system video is played out of a frame buffer and asystem clock controlling the buffer can be altered.

Whatever parameter is actually monitored, the appliance can operate asystem whereby it establishes a threshold level of the switchingparameter. This could be done adaptively by observation. So, forexample, the appliance could monitor power current for the TV over aperiod and find a high range and a low range of power usage(corresponding to on and standby). Having done this it could set thethreshold in the gap between these ranges, for example at the halfwaypoint. In this way, adaptive determination of the threshold is achieved.

Further aspects of the invention provide a power control apparatus foran appliance, an appliance incorporating the power control apparatus anda computer program for controlling operation of the power controlapparatus.

Whilst embodiments in this specification describe a STB, it is to beunderstood that the invention may equally be applied to the powermanagement of other TV peripherals such as DVD players, VCRs and gamesconsoles.

For the purposes of exemplification, there now follows a briefdescription of some embodiments of the invention as shown in theaccompanying Figures of which:

FIG. 1 shows, in flow chart form, the power management method performedby a controller of an appliance in accordance with the invention;

FIG. 2 shows an appliance and television set device for use inperforming a first embodiment of the power management method of theinvention, based on monitoring power supply to the television set;

FIG. 3 shows control functions of the appliance in FIG. 2;

FIG. 4 shows apparatus for performing a second embodiment of theinvention, based on monitoring a LO frequency;

FIG. 5 shows a variant of the second embodiment of the invention;

FIG. 6 shows control functions of the appliance in FIG. 4;

FIG. 7 shows apparatus for performing a third embodiment of theinvention, based on monitoring line scan;

FIG. 8 shows control functions of the appliance in FIG. 7;

FIG. 9 shows a system with multiple appliances of the type shown inFIGS. 7 and 8.

FIG. 1 shows a flow chart for the overall method of power management ofan appliance. Although reference will be made to a set top box (STB),the method is not limited to use with a STB. In step 11, a sensorforming part of a controller system for the STB, monitors acharacteristic parameter of an operating signal associated with thetelevision set, for example, the current associated with the powersupply to the TV set. The controller is programmed to recognise one ormore predetermined values of the measured parameter, for example amaximum and/or or minimum predetermined value (PDV) of the parameterwhich is associated with a recognisable state of the TV set. Where theparameter is the electrical current, the sensor/controller areprogrammed to recognise a minimum value above which the TV set isassumed to be in use, and the STB needed in its ON mode and/or a minimumvalue below which the TV set is assumed to be off or in stand by modeand the STB is required to be in its STAND BY mode. The maximum and/orminimum value (i.e. the predetermined value (PDV)) may be a single valueof current. In step 12, if the sensor detects a change in the parameterwith respect to the PDV (for example, the value of the parameter changesfrom a value above the PDV to a value below the PDV), the controllerproceeds to step 13 and checks whether the current power mode of the STBmatches the desired power mode for the given value of the parameter. Ifthere is not a match, then the controller changes the power mode, atstep 14, to the desired power mode.

As previously discussed, in other embodiments, the PDV may be, forexample a frequency range consistent with frequencies through which theSTB signal is received by the TV set, or a line scan signature unique tothe provider of the broadcast service received by the STB. The powermode is checked whenever the value of the monitored parameter fallsoutside or into the range.

FIGS. 2 and 3 illustrate a first embodiment of the invention. As can beseen, a STB 1 is associated with a TV set 2. The power plug 4 for the TVset 2 is received by a socket 3. The socket 3, in turn, is equipped witha power plug 5 which can be inserted into the mains power supply wherebyto provide power for the STB 1, the socket 3 and the TV set 2. Socket 3includes a sensor, two variations of which are shown in more detail, fordetecting changes in electrical current passing through the socket. Thesensor can take the form of a few turns of wire 23 wound around one ofthe wires in the power feed to the TV (either live or neutral). Thisacts like a small transformer. When the TV is operating, a small 50/60Hz signal is detected 24 and used to provide an output signal 25 forsending to the STB. This technique provides safety isolation from the TVmains supply feed. In another technique, a low resistance component 26is placed in series with one of the lines of the TV power feed. Asbefore, when the TV is operating, a small signal appears acrossresistance 26 which is detected 27 and used to provide an output signal25 for sending to the STB.

The socket is electronically connected with the STB 1 and communicateswith the control unit 6 of the STB. The ‘power detect’ signal 25 can becommunicated with the STB by power line communications signals, wireless(radio, IR) or a direct wired link. Referring to FIG. 3, the controlunit 6 comprises a receiver 28 for receiving the power detect signal 25from the socket 3. A controller 29, such as a microcontroller withcontrol software stored on memory 15, performs the control logic andissues a power control signal to a power stage of the STB to turn theSTB between an ON mode and a standby mode. Memory 15 also storesthreshold levels for use in deciding when the power signal 25 detectedby the sensor in the socket 4 is sufficient to turn the power stage onor off. When the TV set 2 is in its ON mode, it will drain more currentfrom the power supply via the socket 4 than when it is switched off orin reduced power STAND BY mode. As previously discussed, the socket 3communicates changes in current to the controller 6 of the STB 1, whichin turn effects appropriate changes in the power mode of the STB.

The socket 3, including the sensor, and plug 5 can form an integratedunit with the appearance of a mains adapter.

In an alternative arrangement, not shown, the mains plug 4 for the TV isplugged into a socket on the STB, which supplies power looped throughfrom the STB power input. All of the monitoring functions describedabove can then be housed within the STB.

FIGS. 4 to 6 show a second embodiment of the invention wherein a STB 31includes a control unit 33 which is in communication with an RF cable 36which in turn connects with a TV set 32. The TV set 32 also has anaerial 34 through which broadcasts are received, which connects throughthe STB 31, and a mains plug 35. The STB may also have its own powersupply (not shown). The RF cable detects leakage from theoscillator/mixer 37 of the TV set 32 from which the frequency of signalsviewed on the TV set can be determined. In a known manner, the localoscillator 37 generates a LO signal at a frequency which is sufficientto translate the required RF channel down to the tuner's IF frequency.The IF of the tuner is normally around 40 MHz and, as an example, theUHF band used for TV transmission covers the range 470-860 MHz. Thus,the LO frequency to be monitored will differ from this by 40 MHz.

Controller 29 is programmed to recognise as a PDV a frequency, orfrequency range, associated with broadcasts viewed through the STB. Whensuch frequencies are detected, the controller switches the STB to its ONmode. When the detected frequency falls outside the range; thecontroller switches the STB to STAND BY mode. A STB will usually outputa channel, selected by a user on the STB's remote control, on a singleRF channel and the TV will be tuned to that RF channel. In this case,the frequency monitored by the STB is the LO frequency necessary totranslate the RF output channel to the IF of the TV. Frequency valuescan be stored in a memory associated with controller 29.

This technique makes use of the realisation that local oscillatorsignals leak where they shouldn't. Thus, some of the LO signals willreturn from the tuner to the aerial input. Even though the RF cablebetween the STB and TV is screened, the cable passes signals which havealready been picked up within the TV.

In an alternative embodiment, shown in FIG. 5, an internally mountedantenna 40 within the STB is used to detect emissions originating fromthe LO.

FIG. 6 shows control unit 33, with similar features having the samereference numerals as previously shown in FIG. 3.

FIG. 7 shows a third embodiment of the invention. TV sets 32 with acathode ray tube (CRT) type of display use a scanning technique todisplay an image. Line scan in a CRT-based TV is normally magnetic.Taking a PAL signal as an example, the frame rate is 25 Hz and there are625 lines per frame, giving a line rate of 25×625=15.625 KHz. Linedeflection is achieved by passing a waveform at this rate through a coil51 around the neck of the CRT, which deflects the CRT beam from left toright. The consequence of this is that there will normally be asignificant magnetic field detectable even outside the TV set. This is arelatively high power circuit and often, for reasons of economy ofcircuitry, this high power line scan circuit 50 is also used to provideinput to the transformer which generates the EHT voltage (˜25 KV) usedto accelerate the electron beam. Given all of this high power circuitryrunning at the line rate, a signal at the line rate can be detected inSTB 31 positioned near the TV 32. An antenna or magnetic field pick-up55 is housed within the STB 31.

In a further development of this embodiment, the STB modifies the videosignal which is fed to the TV set 32. A control unit for achieving thisis shown in FIG. 8. Controller 29 varies the timing of the linesynchronisation signals in the output video signal to the TV tointroduce a signature. This can be achieved by applying a line synccontrol signal to a line sync processing unit 62. Line scan signals fromthe TV are detected by a pick-up 55 and detection circuit 61. Controller29 monitors the line scan frequency. If perturbations in the line scantiming are the same as those being introduced by the controller 29, thenthe STB knows that the TV is displaying this signal. Similarly, if theperturbations are not detected, the STB knows that the TV is notcurrently displaying the output of the STB. The perturbations must becarefully controlled so as not to unduly affect the synchronisation ofthe TV. Preferably, the line sync pulses which occur during fieldblanking, when no visible material is being transferred, aremanipulated.

The method of monitoring a TV can include two steps. In a first step,controller 29 monitors just for the presence of a line scan, which willindicate whether the TV is displaying a video signal at all. If no linescan is present, then the STB can switch to stand by. However, if a linescan is found, then the controller 29 can begin to introduce a signatureinto the video signal and monitor for the presence of that signature, aspreviously described, to determine whether the video signal beingdisplayed is the signal output from the STB.

FIG. 9 shows a system with three appliances: a STB, a DVD player and agames console. Each appliance can introduce a signature into its videooutput signal 71, 72, 73 and monitor the line scan emissions 52 of theTV to determine whether a video signal with the signature introduced bythe appliance is being displayed by the TV. If the TV is not displayingthe signal, then that appliance can decide to power down.

1. A power control method for an appliance (1) which outputs a videosignal for display on a television set (2), the appliance having an ONpower mode and a STAND BY power mode and being in communication with thetelevision set, the method comprising; monitoring a parameter of anoperating signal associated with the television set (2); comparing thevalue of the parameter with predetermined values at which the applianceis desired to be either operative (ON power mode) or inoperative (STANDBY power mode); and, evaluating, when a predetermined value of theparameter is detected, the current power mode of the appliance (1) andif this is not the desired power mode, initiating a change in operationof the appliance (1) from its current power mode to the desired powermode.
 2. A method as claimed in claim 1 wherein the operating signal isthe electricity supply to the TV set (2).
 3. A method as claimed inclaim 2 wherein the parameter is the current of the electricity supply.4. A method as claimed in claim 3 wherein a predetermined valuecorresponds to a minimum above which the TV set is known to be switchedon.
 5. A method as claimed in claim 1 wherein the operating signal isthe TV signal displayed on the TV set and the parameter is the frequencyat which the signal is received.
 6. A method as claimed in claim 5wherein a predetermined value is the frequency or frequency band atwhich the appliance receives services from the service provider whosebroadcasts the appliance is configured to receive.
 7. A method asclaimed in claim 1 wherein the operating signal is the oscillator/mixersignal of the television set and the predetermined value is thefrequency or frequency band of the oscillator/mixer signal.
 8. A methodas claimed in claim 1 wherein the operating signal is the line scan ofimages displayed by the TV set and the predetermined value is thepresence or absence of a line scan.
 9. A method as claimed in claim 8wherein the line scan incorporates a signature unique to a broadcastservice provider whose services are received through the appliance. 10.A method as claimed in claim 8 wherein the line scan incorporates asignature unique to the appliance.
 11. A method as claimed in claim 9 or10 wherein the predetermined value is the presence or absence of thesignature.
 12. A method as claimed in any one of the preceding claimswherein the predetermined value is adaptive.
 13. A method as claimed inany one of the preceding claims wherein the appliance is a set top box(STB), a DVD player, a VCR or a games console.
 14. A power controlapparatus for an appliance (1) which outputs a video signal for displayon a television set (2), the appliance (1) having an ON power mode and aSTAND BY power mode and being in communication with the television set(2), the apparatus comprising; means for monitoring a parameter of anoperating signal associated with the television set; means for comparingthe value of the parameter with predetermined values at which theappliance is desired to be either operative (ON power mode) orinoperative (STAND BY power mode); and means for evaluating, when apredetermined value of the parameter is detected, the current power modeof the appliance, and if this is not the desired power mode, initiatinga change in operation of the appliance from its current power mode tothe desired power mode.
 15. A power control apparatus as claimed inclaim 14 wherein the operating signal is the electricity supply to theTV set.
 16. A power control apparatus as claimed in claim 15 furthercomprising an electrical socket (3) configured to receive the power plug(4) of the TV set (2), the socket (3) being electrically connectable toa mains electricity supply and including means (23, 24; 26, 27) forsensing changes in one or more characteristic parameters of theelectricity supply passing through the socket and means forcommunicating the sensed changes to the control apparatus.
 17. A powercontrol apparatus as claimed in claim 14 wherein the operating signal isthe TV signal displayed on the TV set and the parameter is the frequencyat which the oscillator/mixer of the TV is operating, the apparatusfurther comprising means (42) for monitoring the frequency or frequencyband to which the oscillator/mixer of the television set is tuned.
 18. Apower control apparatus as claimed in claim 17 wherein the monitoringmeans comprises an RF cable (36) coupling the appliance to thetelevision set.
 19. A power control apparatus as claimed in claim 14wherein the operating signal is the line scan of images displayed by theTV set and the apparatus comprises means for monitoring the line scan.20. A power control apparatus as claimed in claim 17 or 19 wherein themonitoring means comprises an antenna (40, 55) within the appliance. 21.A power control apparatus as claimed in claim 19 which is arranged tocause the appliance to incorporate a signature in the scan rate of thevideo signal which can be monitored by the apparatus.
 22. A computerprogram for causing a power control apparatus to perform the method asclaimed in any one of claims 1 to
 13. 23. An appliance comprising anoutput for outputting a video signal for display on a television set anda power control apparatus as claimed in any one of claims 14 to 21 or acomputer program as claimed in claim
 22. 24. An appliance as claimed inclaim 23 in the form of a set top box (STB), a DVD player, a VCR or agames console.